This is not a medical consultation or advice, only educational information. For any specific questions, talk to your doctor.
EpiPen is an injection of Epinephrine (also called Adrenaline) that is indicated for treatment of anaphylaxis (or anaphylactic shock), which is a clinical representation of the most severe systemic allergic reactions. Anaphylactic shock may have multiple signs and symptoms, such as: urticaria and/or angioedema; bronchospasm; hypotension; cardiac arrhythmias; unconsciousness and shock (this is an incomplete list, see picture and references for more).
All these adverse reactions occur in the context of an IgE-mediated mechanism. IgE is a type of antibody, which is released in huge amounts in the body when a person is exposed to any type of allergen which they are sensitive to following a first exposure (of course, different people may have different allergies; some may have several, some may have none).
When IgE antibodies are released in the body, they cause multiple effects that comprise the anaphylactic shock (some were mentioned above, see references below for others).
Epinephrine is a natural hormone that is responsible for the activation of the sympathetic nervous system. For example, it can cause an increase in heart rate and blood pressure, it can cause dilation of the bronchi (which allows to breathe better) and other effects. For this reason, it is used as a medication for anaphylaxis, since it can reverse many of its symptoms (i.e. hypotension, bronchoconstriction etc.).
It is worth noting that being a natural hormone, if Epinephrine is taken orally, it is broken down in the stomach rather quickly. That is the reason it has to be given by injection.
I will answer some of your questions specifically:
- Epinephrine will usually begin to have an effect in a few minutes, which is important for a medication given for a life-threatening condition (anaphylaxis).
- There are several ways to administer Epinephrine. It is agreed upon that the most beneficial method is to inject it into the thigh muscle.
- Epipen is used to treat anaphylactic shock regardless of the allergy that caused it. No matter which allergen caused the shock, anaphylaxis is the same for all people (it is an immunologic reaction of the human body). Therefore, whether it is caused by exposure to latex, bee sting, milk etc., a person in anaphylactic shock should receive the proper dose of Epinephrine as soon as possible (there is an adult dose of 0.3 mg and a child dose of 0.15 mg).
- For the actual method of administration (which is a very important thing to know, for everyone), you can ask a healthcare professional or watch clips on YouTube, such as this one. (important: one of the things people overlook many times is the fact that you have to inject the medication, HOLD IT IN for 10 seconds and then pull the injector out).
For further information, you can check out the EpiPen official website and the following texts:
Adrenaline in the treatment of anaphylaxis: what is the evidence?
Epinephrine: The Drug of Choice for Anaphylaxis--A Statement of the World Allergy Organization